Its prow angled high, the speedboat skims across an iridescent lagoon that shivers with wind-whipped chop. Just ahead looms the island city of Malé, bustling capital of the Republic of Maldives, about 400 miles southwest of the southern tip of India. Clearly visible is the low line of motorized dhonis tethered in the harbor, and just beyond the boats, a row of multistory buildings that seem to be floating like a mirage. Exactly where, I find myself wondering, does the sea end and the land begin? For Malé--with its crowded shopping streets, its lively fish market, its gold-domed Friday mosque--might just as well have been built on a lily pad, so low does it ride in the water.

Most of the time, that lack of elevation makes no difference. But occasionally it makes a big one--as it did that Sunday morning late last year when waves triggered by the great tsunami of 2004 spilled over sea walls to flood the city with sand-clouded water and then swept out just as suddenly, leaving behind a visceral feeling of foreboding. For what has the more thoughtful of Malé's 80,000 or so residents worried is that such intrusions will become more frequent, not because of the sudden onslaught of tsunamis but as a result of the slow, relentless effects of global warming on the sea that surrounds them.

The 1,192 islands of the Maldives make up what's arguably the lowest-lying country in the world. The average elevation is a little more than 3 ft. above sea level, and what's considered high ground tops out at under 10 ft. Even now, storm surges combined with heavy rains and high tides can be counted upon to cause serious problems somewhere in the country at least once a decade. But people here are haunted by the specter of the disasters to come if--as seems inevitable--greenhouse effects cause sea levels to rise higher and higher. Indeed, it was Maldives' President Maumoon Abdul Gayoom who first raised the issue of global climate change from the perspective of a small island nation to the U.N.'s General Assembly nearly two decades ago.

But even though public awareness about global warming has grown significantly since then--and even though evidence that temperatures are rising now seems incontrovertible--there hasn't been a great deal of progress in dealing with it. Paradoxically, that is partly because of the success of the environmental movement, which celebrates a major milestone this week: the 35th anniversary of the first Earth Day on April 22, 1970. Back then a dedicated band of ecology-minded crusaders set out to save the planet with the same sort of idealistic, confrontational activism that was working so well for Vietnam War protesters and the women's movement.